In general, a short-circuit protection circuit is provided to a driving circuit for a switching element included in a power converter such as an inverter, for the safety reason. The short-circuit protection circuit is required to not only prevent the switching element from being destroyed due to heat which is caused by an overcurrent when a short circuit happens, but also prevent the switching element from being broken down due to a breakdown voltage which is caused by a surge voltage generated when the overcurrent is cut off.
Japanese Patent Application Publication No. 2001-345688 discloses a semiconductor switching element driving circuit. The driving circuit includes an overcurrent limiting circuit and an overcurrent protection circuit. The overcurrent limiting circuit is configured to instantaneously decrease a voltage of a gate terminal once a collector current becomes larger than a first value. The overcurrent protection circuit is configured, first, to decrease the collector current with a first inclination once the collector current becomes larger than a second value, and then, to decrease the collector current with a steep second inclination once the collector current becomes smaller than a third value.
In addition, Japanese Patent No. 3680722 discloses an overcurrent protection circuit of a switching element. The protection circuit includes: a gate voltage holding means for holding a gate voltage at a set value; a gate current increasing means for increasing a gate current temporarily to decrease the gate voltage quickly; and a gate current suppressing means for changing the gate voltage moderately to the set value after the operation of the gate current increasing means.